Update branch handling
Update branch handling

Remove read_properties, the value is not set any more. Instead
depend on proper setting in doc-test.conf if trunk is not used.

Change-Id: Ic28c8313254059f83fea27deab2eba4788f34133

openstack/openstack-doc-tools,savinash47/openstack-doc-tools,openstack/openstack-doc-tools,savinash47/openstack-doc-tools,savinash47/openstack-doc-tools